I wonder if, instead of manually picking a number of XP to add, you could just have a "to next level" option that automatically takes exactly what is needed to get that character to the next level, or as close to as possible with the amount of XP.
Hrm. Maybe I could have it so that there is another window that displaies an option for manual control, or, as you suggest, an automatic "Next Level" option?
*Edit: I kinda like that solution best, actually.
*Edit2: Image updated! I have no idea how/if I can pull off displaying how much EXP players would pay when the cursor's context is on "Next Level". However, I can at least display how much players paid after choosing said option?
Geeze, it's only 10 in the morning, and I wanna go back to sleep.
*Edit3: I... might have figured it out? Probably could use MOR TESTING, though. Later. Later is good.